Plasma power effect on oxygen reduction reactivity of copper/nitrogen-doped graphene core-shell prepared via plasma solution

Abstract

Metal-carbon core-shell nanostructures have gained research interest, due to their valuable properties, such as high reactivity, stability, catalytic, optical, and electrochemical properties. However, the uses of metal-carbon core-shell nanostructures are limited due to the complicated synthesis processes. Therefore, developing a simple and fast method for synthesizing metal-carbon core-shell nanostructures is one of the main targets. In this work, the encapsulation of copper core by a nitrogen-doped graphene shell (Cu-NG) was successfully fabricated using a one-step solution plasma discharge process (SP) at different plasma powers. The structure of the prepared Cu-NG core-shell at different powers was confirmed and verified by X-ray photoelectron microscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), and Raman shift measurements. The structural analyses exhibited a fine core-shell structured nanoparticle with a size range of 5 to 15 nm, dependent on plasma discharge power. Notably, the N-doped graphene shell was favored at low power (120 W). The electrocatalytic activity toward the oxygen reduction reaction (ORR) of the obtained samples in an alkaline solution was acceptable. The effective ORR activity was possibly attributed to the synergistic effect of the copper core and N-doped graphene shell. This study provides eco-friendly and cheap alternative ORR catalysts with acceptable electrocatalytic activity.